When a battery is used improperly, such as overcharge, internal materials of the battery will generate gas by a decomposition reaction due to an excessive voltage. Because the battery's structure is a sealed structure, the internal pressure of the battery will be increased by the generated gas. The temperature of the battery will also be increased due to the phenomena of the decomposition reaction or the energy consumption by the resistance. Therefore, a safety valve is provided in the battery to relieve the pressure before the internal pressure is increased. The safety valve is a kind of stress actuating structure, and known technologies improve the battery design only on the pressure control of the safety valve.